1) Field of the Invention
The present invention relates to a can end for a can, such as an easy opening can, and to such a can provided with at least one such a can end.
Such cans are intended for use as a beverage can and as a food can.
2) Description of Related Art
Generally, beverage cans are thin walled (0.04-0.15 mm). Such a beverage can obtains its strength (after filling and closure) by an internally build up pressure. To that extent the can is filled and provided with gas generating material. After closure, gas formation results in the internal build up of pressure.
Generally, food cans are provided with food which may have to be subjected to a pasteurization or sterilization procedure. Accordingly, pressure build up may be temporary during such procedure. However, due to undesired circumstances bacterial growth might result in internal pressure build up after the food can was filled and closed.
In relation to both food cans and beverage cans improper processing filling and handling of such cans may result in temporary or continuous pressure build up which may result in a deformation of in particular the can closure at the top end and/or the bottom end. Accordingly, overfilling the can with the content material, too high processing temperatures, unsatisfactory cooling operations, insufficient vacuum drawing in the can, pre-process spoilage of content, gas formation due to an undesired reaction between can metal and the content resulting in gas formation such as hydrogen gas, and incorrect handling resulting in impacting on the can may result in continuous or temporary pressure build up. These pressure build ups may result in a deformation of the can ends to an extent dependent on the pressure build up.
One form of localized distortion of the can end is buckling or pleating resulting in a local distortion which could extent into the counter sink and seaming region. The bulked portion may even locally extent beyond the perimeter of the can. Higher pressure build up may result in bulging or even the formation of a so called springer. Such bulges may be forced back into the normal can end position. A hard blow will result in a severe and permanent outbulging of one or both ends of the can.
In this respect it is noted that can ends may be designed such that due to pressure build up the concave can end flips out into a convex form (see for instance EP 0 906 222).